There has been used an organic EL device that for example includes, above a glass substrate, a display unit having an organic EL layer between an anode and a cathode.
In recent years, there has been a demand for an organic EL display device that is excellent in terms of design and mobility. An organic EL display device having an excellent design for example includes a display unit that is curved. An organic EL display device having an excellent mobility for example has a further reduced weight.
In response to the above demand, a technology has been proposed that uses a resin substrate (a resin film) having flexibility for an organic EL display device instead of a glass substrate (for example, Patent Literature 1). However, the resin substrate exhibits a low barrier property against moisture. For this reason, moisture intrusion into an organic EL layer through the resin substrate might change luminescent color, or even worse, might disable light emission.
In view of this, a technology has been proposed that prevents moisture intrusion into a display unit (organic EL layer) by providing a hygroscopic layer between a resin substrate and the display unit to absorb moisture (for example, Patent Literature 2).
The hygroscopic layer has a hygroscopic film that is sandwiched between a pair of covering films. The covering films are made of a material whose moisture vapor transmission rate, which indicates a degree of moisture transmission, is low. The hygroscopic layer prevents transmission of moisture through the covering films, and absorbs moisture, which has intruded through the covering films, and thereby to prevent intrusion of the moisture into the display unit. Note that the hygroscopic layer is referred to also as a waterproof layer having a waterproof property because of preventing moisture intrusion into the display unit.